The Effect of Rejuvenation on the Balance Between Polymer Degradation and Bitumen Ageing Considering Different Polymer Contents

Currently, recycling reclaimed polymer-modified asphalt from surface layers for the primary road network in Belgium and other European countries is still prohibited. This chapter addresses the influence of different amounts of styrene–butadiene–styrene (SBS) as a modifier on the balance between polymer degradation and bitumen ageing in order to gain better insights into the potential reuse of such binders. Moreover, it explores the role of rejuvenation in these synchronous phenomena, utilising meaningful rheological performance parameters, assessed using a dynamic shear rheometer (DSR) as well as chemical ageing and polymer indices via Fourier transform infrared (FTIR) spectroscopy. To elucidate these challenges, the ageing process was followed in the lab with the standardised short-term ageing simulation of the rolling thin-film oven test (RTFOT) and kinetics in the long term by means of modified thin-film oven testing (MTFOT). The findings show a greater resilience against ageing for higher SBS content based on rheological parameters such as the Glover–Rowe (G-R) and crossover frequency. It also appears that polymer degradation dominates in short-term ageing, while bitumen oxidation outplays polymer degradation in the long term for high-content polymer-modified bitumen (PMB). This study also demonstrates that the implementation of a rejuvenator has shown a promising effect on short-term ageing, based on most rheological, distress-related parameters. Finally, FTIR clearly captures the effect of a rejuvenator on bitumen ageing; however, its effects on polymer degradation are less distinct. All in all, this work is rather encouraging when it comes to the potential reuse of PMBs by thoroughly studying their chemomechanics considering different SBS contents.